In many angiosperm species, especially those adapted to temperate regions, the leaves fall in the fall and are reborn in the spring.
Plants that lose leaves in a certain season are called deciduous or deciduous. Plants that do not lose their leaves are called perennials.
Falling leaves in the fall is interpreted as a adaptation to intense cold and snow. Instead of having the leaves damaged by the winter cold, the plant drops them "deliberately" in the fall, in a process it controls.
Leaf fall occurs through a process called leaf abscess. Initially, scar tissue forms in the region of the petiole that connects the leaf to the stem, the abscission tissue, which gradually interrupts the passage of water and mineral nutrients from the stem to the leaf. The plant thus loses the leaves with minimal damage and reduces metabolic activity throughout the winter. In spring, new leaf beginnings appear alongside dormant buds, which soon develop into leaves.
Sheets can be classified in several ways: according to its arrangement in the stem, the shape of the limb, the shape of the edge etc.
Philotaxis is the way the leaves are arranged on the stem. There are three basic types of philotaxis: opposite, vertical and alternate.
Philotaxis is opposite when there are two sheets per node, inserted in opposite regions. When three or more sheets are inserted into the same node, philotaxis is called verticilated. When the leaves are inserted in slightly displaced regions on successive nodes, describing a helix, the phyllotaxis is called alternate.
Limbo can be simple (undivided) or compound, divided into two, three or more leaflets. If the leaflets of a compound limb all start from the same point of the petiole, arranged like the fingers of one hand, the leaf is called spanking.
When the leaflets dispose throughout the petiole, the leaf is called the bump. Penetrated leaves can end in a single leaflage and are called deprived, or in two leaflets, being called paripenadas.
The shape and border type of the limbus are other characteristics used in leaf classification.